Energy-saving heavy crude oil emulsion-treating apparatus

ABSTRACT

A treater for electrostatically separating emulsified water from oil during longitudinal flow through a horizontally elongated coalescing section has a number of baffles with adjacent electrostatic wing grids therein. The electrostatic wing grids are externally connected to two or more transformers so that a higher voltage may be applied to subsequent grids along the coalescing section. Each of the electrostatic wing grids includes a front face and perpendicular side edges and a perpendicular bottom edge to extend the electrostatic field out beyond the front face, so as to enhance the electrostatic action and more efficiently remove water from the emulsion. The baffles preferably extend downwardly to a water/oil interface, so as to increase the efficiency of the emulsion flowing through the coalescing section and ensure that the electrostatic field is applied to the emulsion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to emulsion-treating (dehydration)apparatus, and, more particularly, to an improved energy-conservingelectrostatic coalescer for separating emulsified brine from oil duringlongitudinal flow through a horizontally elongated metal tank.

2. Description of Related Art

It is well known that petroleum as it is naturally produced from anunderground formation must be treated so as to separate and removeentrained gas and emulsified brine or water, in order to render the oilpipelineable. Various techniques and processes have heretofore beenemployed in order to minimize treatment time and avoid high-energyconsumption. In particular, U.S. Pat. No. 4,329,159 (“'159”) to Bull,entitled, “Energy Saving Heavy Crude Oil Emulsion Treating Method andApparatus for Use Therewith” describes a method and apparatus comprisingan elongated horizontal cylindrical tank, divided by internalpartitions, into compartments through which the petroleum willsequentially flow. Burner-fired heaters are normally included in anupstream heater section for heating the emulsion to a desiredtemperature, during which most of the entrained gas and some of thebrine will separate from the emulsion. The partially de-emulsified brinethen flows into a coalescing section, encountering a series of bafflesadapted to encourage even flow of fluids and to avoid the formation offlow channels within the fluid body. Additionally, high-potentialelectrostatic fields are applied by energizing grids with high voltagepotential. The grids are adjacent to each grounded baffle, which createsthe fields between each grid and grounded baffle. The resultantelectrostatic fields coalesce the droplets of brine remaining in the oilinto drops of sufficient size and weight that they flow downwardly bygravity to the bottom of the coalescing section for removal. Oilsubstantially free of brine, then flows over a wall into a reservoirwhere the brine-free oil may be intermittently or continuouslydischarged, without affecting the liquid level in the treater.

While the use of the baffles and the electrostatic elements in the '159patent have resulted in enhanced separation of the oil and brine, theinvention herein described discloses further improvements in which themetallic apertured grids have been expanded so as to take up more of theflow area, and include longitudinally-extending sections or wings thatprovide a more even and larger electrostatic zone between the grid edgesand the wall of the vessel (grounded) to improve the coalescence of thebrine within the emulsion flowing through the treater.

In addition, to further improve and enhance the separation of the oiland brine, the present invention includes the use of multipletransformers. After conducting a number of experiments, it was foundthat wet emulsion is much more conductive than lean (dry) emulsion, andwill, therefore, draw a much larger current through it as it flowsthrough an electrostatic field. That is, an emulsion flowing through acoalescing section entering a first electrostatic field will contain themost brine and, therefore, the first electrostatic field will draw thehighest current. This current load will then determine or set theapplied voltage to all the grids in known electrostatic coalescers,because there is only one power feed from a single transformer usedtherein. The transformers, used to supply high-voltage to theelectrostatic grids in known treaters, are self-protected (reactive),and, therefore, reduce the output voltage as the current increases.Brine droplets in a wet emulsion will coalesce very easily under a weakelectrostatic field, because the droplet population density is high andthe space between droplets is small. Therefore, reduced voltage on afirst grid does not hamper the coalescing action. However, as theemulsion travels through the coalescing section and the brine iscoalesced therefrom, the reduced voltage on the subsequent electrostaticgrids reduces the effectiveness of the applied electrostatic fields. Thesequentially leaner emulsion traveling through the sequential grids in atreater actually requires much stronger electrostatic fields to coalescemore widely-dispersed brine droplets contained in the emulsion beingtreated. The emulsion flowing from a first electrostatic grid-tosubsequent electrostatic grids becomes drier as water coalesces and isseparated out. Therefore, in order to sustain effective coalescing ateach electrostatic field, the present invention increases the voltage ateach sequential grid. This is provided by using two or more transformersand power feeds to the electrostatic grids. Each electrostatic grid andtransformer is operated independently, and is set at a differentvoltage. That is, the first stage grid will be set at a low voltage tohandle wet emulsion, while the subsequent grids would be set atincreasingly higher voltages to handle leaner emulsions as the emulsiontravels through the coalescing section. The last field in the serieswill coalesce the last small quantities of water or brine remaining inthe oil emulsion, by having the highest voltage applied thereto.

The present invention also has the baffles before each electrostaticgrid extending all the way down to the oil/water interface in thetreater section, to overcome the problem found with the '159 patenttechnology. That is, wet emulsion tends to bypass the electrostaticfield zone by flowing under the baffles and electrostatic grids, alongthe surface of the oil/water interface. By lowering the ends of thebaffles to the oil/water interface, the hydraulic bypassing is reduced,and thereby increasing the efficiency and effectiveness of the presentinvention.

In addition, in a further embodiment of the present invention, a firstdistribution baffle, before the first electrostatic grid, is providedwith circular holes in an offset triangular pattern with a total openarea of 8%-16%. These circular holes in the triangular pattern promotemore uniform horizontal plug flow of the emulsion through the treater,so that all of the emulsion is exposed to the electrostatic fieldsuniformly.

Therefore, it can be seen that the present invention meets an existingneed in the art for the improved and more efficient treating ofemulsified oil as it flows through a treater section by the use ofimproved electrostatic grids, the application of increasing voltage tosequential grids, together with improved and modified baffles for bettercontrolling the flow of the emulsion through the treater.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to providean improved apparatus for treating (dehydrating) an emulsion. It is aprinciple object of the present invention to provide an improvedapparatus for more efficiently treating oil, gas, water emulsionsflowing through a coalescing section of a treater. It is anotherparticular object of the present invention to provide improvedelectrostatic elements for more effectively coalescing out droplets ofbrine in an oil/brine emulsion flowing through a coalescing section of atreater. It is yet another particular object of the present invention toprovide an improved apparatus for achieving substantially completeseparation of brine from oil by utilizing improved electrostaticelements having wing sections thereon. And, it is a further particularobject of the present invention to provide an improved electrostaticcoalescer having more efficient electrostatic elements, elongated baffleelements used in conjunction with such electrostatic elements, andvariable voltage means to apply varying voltages to sequentially-placedelectrostatic elements in a horizontal separating vessel.

These and other objects and advantages of the present invention areachieved by providing a horizontal vessel comprised of at least acoalescing section. The coalescing section has a plurality ofelectrostatic grids suspended therein adjacent to a plurality of bafflesextending entirely across the flow path of an emulsion travelinglongitudinally through the horizontal vessel. The electrostatic gridelements are comprised of wing-type grids, having a plurality of edges,which extend longitudinally along the flow path to increase theelectrostatic efficiency thereof. In a second embodiment of the presentinvention there is provided a plurality of transformer means forproviding different voltages to the sequentially-spaced grids so as toincrease the efficiency thereof in separating emulsified water from theflowing oil.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention, which are believed tobe novel, are set forth with particularity in the appended claims. Thepresent invention, both as to its organization and manner of operation,together with further objects and advantages, may best be understood byreference to the following description, taken in connection with theaccompanying drawings, wherein:

FIG. 1 is a partial cross sectional perspective view through acoalescing section of a horizontally-extending elongated tank oiltreater showing a preferred embodiment of a plurality of improvedelectrostatic grids adjacent to improved baffles of the presentinvention;

FIG. 2 is a partial side elevational view of the coalescing section ofFIG. 1; and

FIG. 3 is an enlarged, perspective view of one of the wing electrostaticgrid elements of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is provided to enable any person skilled inthe art to make and use the invention and sets forth the best modescontemplated by the inventors of carrying out their invention. Variousmodifications, however, will remain readily apparent to those skilled inthe art, since the generic principles of the present invention have beendefined herein specifically to provide for an improved and simplifiedemulsion treater (hereinafter referred to as a “TREATER”), which may ormay not have a heater section such as set forth in U.S. Pat. No.4,329,159 (“'159”) to Bull. The present invention is an improvement tothe coalescing apparatus set forth in the '159 patent, the disclosure ofwhich '159 patent is incorporated herein, in its entirety, by thisreference thereto. While treatment of crude oil is described as theprimary use for this invention, it is to be understood that it is alsoapplicable in treating and/or coalescing any liquid medium that requiresflow control in a horizontal direction.

Referring now to the drawings, the present invention is utilized in anelongated, horizontal metal tank or vessel 10 of the type disclosed inthe '159 patent. This elongated vessel 10 may have a first heatersection, only part of which is shown, or may consist only of a treatmentor coalescing section 14. If a heater section is used, the coalescingsection 14 is separated by a bulkhead 18 from the heater section. Afoam-removing assembly 52 is disposed in the coalescing section 14,downstream of the bulkhead 18.

The apparatus of the present invention provides a more efficaciousseparation of a viscous emulsion E into its respective components,namely, produced brine B (salt water, heavy mineralized water or freshwater), gas G, and substantially brine or water-free oil O, which exitsthe coalescing section at the second end of 14 through a gas outlet 48,brine-free oil outlet 50 and a brine outlet 46, in the same manner asdisclosed in the '159 patent. This more efficient and improvedcoalescense is accomplished by the use of a plurality of electrostaticwing grids 16, 20, 22, 24, having a plurality of novel baffles 26, 28,30, 32 placed adjacent thereto and either in front of or behind(upstream or downstream) of the wing grids. It is to be understood, thattwo or more grids may be used in the present invention. Each of theelectrostatic wing grids 16, 20, 22, 24 are powered by one or moretransformers 34, which apply the lowest voltage to handle wet emulsionat wing grid 16, a higher voltage at wing grid 20, a still highervoltage at wing grid 22, and the maximum desired voltage at wing grid 24to handle the very lean emulsion and coalesce the remaining smallquantities of brine left in the emulsion as it passes through baffle 32and wing grid 24. That is, the emulsion E traveling from the bulkhead 18to the downstream or outer end of the coalescing section 14 is subjectedto increasingly strong electrostatic fields by the electrostatic winggrids, to more efficiently remove the brine therefrom, and produce asubstantially brine-free oil for exiting through the outlet 50. Inmultiple transformer installations, with many grids, each transformermay be connected to 2 or 3 grids.

The first baffle 26 is preferably provided with circular holes in anoffset triangular pattern indicated by 44, with a total open area of8%-16% of the total area of the baffle 26. This promotes more uniformhorizontal plug flow through the baffle and the first electrostatic winggrid 16, as well as the remaining baffles 28, 30, 32 and wing grids 20,22, 24 so that the emulsion E is exposed to the increasingly strongelectrostatic fields, more uniformly, as it flows through the treatersection 14.

Turning now to FIG. 3, there shown is a preferred embodiment of anelectrostatic wing grid, such as 16, having an enlarged vertical surface36, which is totally immersed in the emulsion E, and which preferably isheld parallel to the baffle 26 in a predetermined spaced relationship(typically 3″-9″). This enlarged vertical surface 36 preferably hascurved outer ends or sides (to conform to the shape of the coalescingsection 14), and flat bottom and top portions, which must be held awayfrom the oil/gas interface and the oil/water interface traveling throughthe coalescing section 14 so that no short circuits occur. The twocurved ends, and the bottom of the enlarged vertical surface 36 areprovided with longitudinally extending portions or wings 38, 40, 42.That is, portions 38, 40 and 42 are referred to as wings, which extendperpendicularly to the enlarged vertical surface 36, for a limiteddistance, depending on the spacing of the grids and baffles(approximately 3″-9″) from each other, so as to provide an enhancedelectrostatic field which extends perpendicularly to the enlargedvertical surface and along the lines of flow of the emulsion through thecoalescing section 14. With this configuration, the electrostatic fieldis axially extended beyond the enlarged vertical face or surface 36, soas to improve the coalescence of brine or water within the emulsionflowing through each grid 16, 20, 22, 24. The wing extensions 38, 40 and42, together with the increased voltage applied to the sequential winggrids 20, 22 and 24 provide better and more efficient results incoalescing substantially all droplets of brine/water suspended withinthe emulsion E to provide a substantially brine/water-free oil O at theoutlet end of the coalescer 14.

The baffles 26, 28, 30, 32 of the present invention extend all the wayto the inner walls, and down to the oil/brine water interface, while theelectrostatic grids 16, 20, 22 and 24 must be spaced approximately 3″-9″away from the internal walls of the coalescer 14, and approximately 6inches to 12 inches above the oil/water interface to prevent anypossibility of short circuiting of the grids. The baffles, except forthe first baffle 26, are preferably open-wire mesh, so as to besubstantially hydraulically invisible. High-voltage varying from about600-1,000 v/in (volts per inch of space between grid and baffle) at thefirst electrostatic wing grid 16, to about 4,000 v/in at the lastelectrostatic wing grid 24, is applied by the transformers 34. Thelongitudinally extending wing portions of the grids provide a secondaryfield along the sides and bottom of the emulsion traveling through thecoalescer 14, providing what may be called a “perimeter zone”, fortreating the emulsion, after it passes by each of the wing grid frontfaces or surfaces. It is to be understood that the transformers 34 are aplurality of separate transformers, which are connected to each of thesequentially mounted electrostatic wing grids, so as to provide thedesired voltages to each grid. In a preferred embodiment of theinvention, two transformers and separate power feeds to dual adjacentelectrostatic grids are used with each of the transformers operatingindependently, so as to set the different voltages for the grids.

It, therefore, can be seen that the electrostatic grids of the presentinvention provide and/or produce improved electrostatic fields tothereby improve dehydration performance of an emulsion, such aspetroleum passing therethrough. Because the wing grids are not flat, butinclude extending side edges or portions, they provide more even andlarger electrostatic zones between the grid edges and the grounded wallof the vessel. Additionally, the application of higher voltages tosubsequent wing grids sustains the effective coalescing action at eachgrid because the increased voltage is applied to a progressively leaneremulsion. Furthermore, the extending of the baffles down to theoil/water interface reduces hydraulic bypassing of the electrostaticzone, while the providing of the first distribution baffle with anoffset triangular pattern over only approximately 8%-16% of its totalarea promotes more uniform, horizontal flow of the emulsion so that allof the emulsion is exposed to the progressively stronger electrostaticfield, in a uniform manner.

Those skilled in the art will appreciate that various adaptations andmodifications of the just-described preferred embodiments can beconfigured without departing from the scope and spirit of the invention.Therefore, it is to be understood that, within the scope of the appendedclaims, the invention may be practiced other than as specificallydescribed herein.

What is claimed is:
 1. An emulsion separating treater for separatingemulsified water droplets from an emulsion, the emulsion separatingtreater, including a generally elongated metal tank constructed andarranged for flow of emulsion therethrough, and comprising a coalescingsection having the following elements in combination: a plurality ofbaffles supported within the coalescing section in spaced relationship;a plurality of sequential electrostatic grid elements supported withinthe treater section and adjacent to the plurality of baffles; means forproviding high voltage to each of the plurality of sequentialelectrostatic grid elements; and wherein each of the plurality ofsequential electrostatic grid elements includes a plurality of wingelements extending perpendicularly to an enlarged face portion thereofalong and parallel to a longitudinal axis of the treater section toprovide an electrostatic zone between each of the plurality of wingelements, an interior wall of the coalescing section, and an oil/waterinterface.
 2. The treater of claim 1 wherein there are three wingelements, two of the three wing elements being connected to side edgesof the enlarged face portion and one of the three wing elements beingconnected to a bottom edge of the enlarged face portion.
 3. The treaterof claim 2 wherein the means for providing voltage is comprised of aplurality of transformers electrically connected to at least one of theplurality of sequential electrostatic grid elements so that asequentially increasing voltage is applied to the plurality ofsequential electrostatic grid elements as the emulsion passes throughthe coalescing section.
 4. The treater of claim 3 wherein each of theplurality of baffles extends downwardly to the oil/water interface inthe coalescing section so as to prevent the emulsion flowing through thecoalescing section from bypassing an electrostatic zone for each of theplurality of sequential electrostatic grid elements.
 5. The treater ofclaim 4 wherein a first of the plurality of baffles in the treatersection includes a plurality of circular holes in an offset triangularpattern with a total open area of approximately 8%-16% of the entirearea of the first baffle, so as to promote more uniform, horizontal plugflow through the first baffle and the coalescing section.
 6. A treaterfor separating emulsified water droplets from an emulsion of water andoil, which separating treater includes a generally elongated metal tankconstructed and arranged for flow of the emulsion therethrough,comprising, in combination: a heater section and a coalescing section; aplurality of sequentially mounted baffles extending generally between anupper surface and a lower surface of an emulsion zone in the coalescingsection; a plurality of sequentially mounted electrostatic wing gridsplaced adjacent to the plurality of sequentially mounted baffles so asto apply a series of electrostatic fields to the emulsion travelingthrough the coalescing section; each of the plurality of sequentiallymounted electrostatic wing grids include longitudinally extending wingportions which are perpendicular to an enlarged face portion; the wingportions being connected to edges of the enlarged face portion, andbeing substantially parallel to a longitudinal axis of the coalescingsection; and a plurality of transformers connected to the plurality ofsequentially mounted electrostatic wing grids for applying a differentvoltage to each of the plurality of sequentially mounted electrostaticwing grids, which different voltage increases at each of the pluralityof sequentially mounted electrostatic wing grids as the emulsion travelsthrough the coalescing section from an upstream end adjacent the heatersection to a downstream end, away from the heater section.
 7. Thetreater of claim 6 wherein there are three wing elements, two of whichare connected to side edges of the enlarged face portion and one ofwhich is connected to a bottom edge of the enlarged face portion.
 8. Thetreater of claim 7 wherein a first of the plurality of sequentiallymounted baffles includes a plurality of circular holes formed in anoffset triangular pattern so as to form a total open area ofapproximately 8%-16% of the total area of the first of the plurality ofsequentially mounted baffles.
 9. An emulsion separating treater forseparating emulsified water droplets from an oil/water emulsion, theemulsion separating treater including a generally elongated metal tankconstructed and arranged for flow of the oil/water emulsiontherethrough, and wherein the emulsion separating treater has a heatersection and a coalescing section, with the coalescing sectioncomprising: a first upstream end adjacent the heater section and asecond downstream end, away from the heater section; a plurality ofbaffles sequentially mounted in the coalescing section between the firstupstream end and the second downstream end; a plurality of electrostaticwing grids sequentially mounted in the coalescing section; one of theplurality of electrostatic wing grids being held adjacent to each of theplurality of sequentially mounted baffles, between the first upstreamend and the second downstream end; each of the plurality ofelectrostatic wing grids including an enlarged front face andlongitudinally extending edge portions, which longitudinally extendingedge portions are substantially parallel to a longitudinal axis of thecoalescing section; each of the plurality of baffles extending down toan oil/water interface in the coalescing section; and a plurality oftransformers connected to the plurality of electrostatic wing grids soas to provide increasing voltage to the plurality of electrostatic gridsas the emulsion travels from the first upstream end to the seconddownstream end.
 10. The treater of claim 9 wherein there are three wingelements, two of the three wing elements being connected to side edgeportions of the enlarged face portion and one of the three wing elementsbeing connected to a bottom edge portion of the enlarged face portion.11. The treater of claim 10 wherein a first of the plurality of bafflesincludes a plurality of circular holes formed in an offset triangularpattern so as to form a total open area of approximately 8%-16% of thetotal area of the first of the plurality of baffles.